1. Field of the Invention
The present invention relates to an improvement in a combination visbreaking and hydrorefining process for upgrading hydrocarbonaceous oils.
2. Description of the Prior Art
Visbreaking is a well-known mild thermal cracking process to which heavy hydrocarbonaceous oils may be subjected to reduce their viscosity by depolymerization and cracking in the liquid phase. See, for example, Hydrocarbon Processing, September 1978, page 106.
The term "hydrorefining" is used herein to designate a catalytic treatment conducted in the presence of added hydrogen, of a hydrocarbonaceous oil to upgrade the oil by eliminating or reducing the concentration of contaminants in the oil such as sulfur compounds, nitrogenous compounds and metal contaminants, hydrogenation of unsaturated constituents of the oil and conversion of at least a portion of the heavy constituents of the oil.
U.S. Pat. No. 2,321,841 discloses visbreaking a heavy hydrocarbonaceous oil and thereafter nondestructively catalytically hydrogenating the visbroken oil. The hydrogenated bottoms may be recycled to the visbreaking zone.
U.S. Pat. No. 3,338,818 discloses hydrovisbreaking a hydrocarbonaceous oil. The lighter fraction of the hydrovisbroken oil is catalytically hydrogenated. The hydrogenated bottoms are recycled to the hydrovisbreaking zone.
U.S. Pat. No. 3,050,457 discloses hydrovisbreaking a crude shale oil and catalytically hydrogenating the light fraction. The overhead gases are recycled from the hydrogenation zone to the hydrovisbreaking zone.
U.S. Pat. No. 3,132,088 discloses visbreaking a residual oil and catalytically hydrogenating the deasphalted bottoms of the visbroken oil.
It has now been found that a combination visbreaking, hydrorefining at conditions to convert at least a portion of the heavy constituents of the visbroken oil and a recycling of the hydrorefined bottoms to the visbreaking zone will provide advantages that will become apparent in the ensuing description.